Higher excited states of benzene: Symmetry assignments of six gerade Rydberg series by four-photon absorption spectroscopy

S. G. Grubb, C. E. Otis, R. L. Whetten, E. R. Grant, A. C. Albrecht

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27 Scopus citations

Abstract

We report the observation of six gerade Rydberg series in benzene converging to the first ionization potential, seen in the region from 14 500-18 500 cm-1 as four-photon resonances in the five-photon ionization spectrum of the jet-cooled molecule. Polarization ratios measured for each transition in two- as well as four-photon resonance aid in determining excited state symmetries. We assign a Rydberg series with a quantum defect of 0.76 to higher members of the 3s Rydberg state first seen by Johnson in the near UV two-photon resonant three-photon ionization spectrum of benzene. The observed quantum defect, polarization ratios, and correlation with synchrotron absorption data all strongly support this assignment. Another series, with a quantum defect of 0.24, exhibits a polarization ratio of 4.5±0.5 signifying pure rank four activity. This is the first report of a purely rank four transition in a molecule. We assign this as an excitation to a d2 orbital which when converging to the first ionization potential (the 2E 1g cation) gives rise to B1g and B2g Rydberg transitions. Within the D6h point group, these symmetries are allowed only in a four-photon transition. The number of gerade Rydberg series observed as four-photon resonances exceeds those available from the s-(1) and d-(3) bound members of a hydrogenic basis set. The participation of g(l=4) orbitale is indicated as the lowest members of two of the Rydberg series are at the n=5 level.

Original languageEnglish (US)
Pages (from-to)1135-1146
Number of pages12
JournalThe Journal of Chemical Physics
Volume82
Issue number3
DOIs
StatePublished - 1985
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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